More control over particles in Phoenix

[vklein]

Would be very helpfull to get particles / cloth to float in Phoenix fluids (which works with "fluid force" quite good now), but also make them buoyant/ constantly raising to the top of the liquid.
Using + gravity don't constrain the particles to only the liquid, they drift upwards leaving the fluid.
Also being able to read and constrain modifiers to value ranges inside the grid would be very helpful (via custom properties?). 
For instance constrain modifiers on particles to:

- main: inside/outside the liquid / smoke / fire
- to certain depth / pressure range in fluid
- only in very turbulent cells
- only in distinctive RGB colored cells

constraining "fluid force" onto inside the fluid would be a main request

by the way, many thanks for introducing my object "collection" request back a few versions, and fixing the VrayMetaballs with tyflow cache problems.

[tyFlow]

I'm not sure if there's a way to calculate buoyancy like that within a PhoenixFD grid. I'd have to talk to the ChaosGroup team about that.

As for your other requests, they can all be achieved with the script operator reading properties saved by the Fluid Properties operator, or by doing neighbor tests on particles driven by the liquid particles of a PhoenixFD grid. I think they're a little too esoteric to have as features in a specific operator.

[vklein]

I'm trying to program it all myself, which should be easy right?
Very rough start without things like inertia or water drag:

Using fluid properties:
- vel = fluid velocity vector
- in = RGB for deciding if in/out of white water (fluid RGB in Phoenix set to white)

if RGB.B>0.99 set in to 1 else 0
If in water set particle velocity vector to vel + buoyancy upward vector
if not then ignore vel and add gravity to particle.velocity

found a bug in fluid properties -> velocity vector

http://forum.tyflow.com/thread-793.html

[tyFlow]

Thank you, I've found the bug and it will be fixed soon.